A molten salt community framework for predictive modelling of critical characteristics

目前包括美国和英国在内的许多国家正在考虑的现有和先进核燃料循环使用的核燃料(UNF)通常在熔融盐(例如LiCl-KCl)中加工，比铀更活跃的裂变产物和(活化的)腐蚀产物元素以溶解离子(例如Co2+、Nd3+、Pr3+和Cs+)的形式在熔融盐中积累。这些元素需要定期移除，以确保工艺安全，回收盐，并最大限度地减少核废料的产生。然而，与这些盐的热力学、物理和化学性质以及作为其在使用中的演变的函数的在役行为有关的关键知识差距--例如，裂变产物和氡系元素的含量与蒸发/腐蚀行为相结合，可以实时动态地改变这些熔融盐的组成，从而改变其关键性质。事实上，即使是简单的相关系，在含有盐的裂变产物/榄系元素中也很难理解。为了充分处理、回收和处置这种核废料以及回收铀和超铀金属等有价值的元素，需要了解熔融盐的热化学和物理知识。然而，这些知识是有限的，特别是对于复杂的盐，如含镧系元素的LiCl-KCl盐，氧化物污染，碱(Na，Rb，Cs)和碱土(Sr，Ba)元素。在拟议的项目中，选择扩展的LiCl-NaCl-KCl-RbcL-SrCl2-BaCl2-LnCl3(Ln=La，Ce，Pr，Nd，Sm和Y)体系作为主要模型体系，使用我们的开源平台，包括ML模型，高通量DFT第一原理计算，MD和AIMD模拟，来加速对结构、热力学和物理性质的探索以及使用UNIQUC和MQM模型的高吞吐量CALPHAD建模。英国的合作伙伴还将致力于进一步研究LiCl-Li2O-(RbcL、CsCl2、SrCl2和BaCl2)，它是电还原火法处理盐的代表，以及(LiF-NaF-KF和LiF-BeF2)，它代表美国和英国的候选熔盐反应堆(MSR)燃料/冷却剂盐。我们拟议的美英合作研究将通过实施先进的热力学模型来制定一个计算框架，以系统地探索关键的熔盐特性，解决与未来快速核反应堆和先进的未来核燃料循环相关的熔盐方面的关键全球知识空白。拟议的研究不仅与美国NEUP Call Workscope FC-1.2直接相关，而且与相应的英国EPSRC Call和更广泛的英国民用核计划有关。该项目将提供各种开源、高吞吐量的计算方法和工具，并支持数据集，以模拟和设计先进的熔盐，对全球熔盐社区具有真正的重要意义。

Used nuclear fuel (UNF) for both existing and advanced nuclear fuel cycles currently under consideration in many countries, including the US and UK, is usually processed in molten salt (e.g., LiCl-KCl), and fission product and (activated) corrosion product elements that are more active than uranium accumulate in the molten salt as dissolved ions (e.g., Co2+, Nd3+, Pr3+, and Cs+). These elements need to be periodically removed to ensure process safety, recycle the salt, and minimize nuclear waste generation. However, there is a critical knowledge gap associated with the thermodynamics, physical and chemical properties, and in-service behaviour of these salts as a function of their evolution in-service - for example, fission product and actinide content, combined with evaporation / corrosion behaviour, can dynamically alter, in real-time, the composition and therefore critical properties of these molten salts. Indeed, even simple phase relations are poorly understood in fission product / actinide containing salts. For adequate treatment, recycle, and disposal of this nuclear waste stream plus recovering valuable elements such as uranium and transuranic metals, thermochemical and physical knowledge of molten salts is required. However, this knowledge is limited, especially for complex salts, such as LiCl-KCl salts involving lanthanide and actinide elements, oxide contamination, and alkali (Na, Rb, Cs) and alkaline earth (Sr, Ba) elements.In the proposed project, the extended LiCl-NaCl-KCl-RbCl-CsCl-SrCl2-BaCl2-LnCl3 (Ln = La, Ce, Pr, Nd, Sm, and Y) system has been selected as the primary model system to demonstrate accelerated exploration of structural, thermodynamic, and physical properties using our open-source platform including ML models, high throughput DFT-based first-principles calculations, MD and AIMD simulations, and high throughput CALPHAD modeling using UNIQUC and MQM models. The UK partners will also aim to further study LiCl-Li2O-(RbCl, CsCl, SrCl2, and BaCl2), representative of electroreducer pyro-processing salts, and (LiF-NaF-KF and LiF-BeF2), representative of the US and UK candidate molten salt reactor (MSR) fuel / coolant salts.Our proposed US/UK collaborative research will develop a computational framework by implementing advanced thermodynamic models to systematically explore critical molten salt characteristics, addressing a critical global knowledge gap in molten salts relevant to future fast nuclear reactors and advanced future nuclear fuel cycles. The proposed research is not only directly relevant to the US NEUP Call Workscope FC-1.2, but also to the corresponding UK EPSRC Call and the wider UK civil nuclear programme. This project will be truly significant for the global molten salt community by providing various open source, high throughput computational approaches and tools, and underpinning datasets, to model and design advanced molten salts.